1. Field
Example Embodiments relate to an internal circuit of semiconductor memory device and, for example, to a boosting voltage generating circuit of a semiconductor memory device.
2. Description of Related Art
In a semiconductor memory device, a boosting voltage VPP may be used for preventing a voltage drop of a transferred signal. The boosting voltage VPP may be higher than an external supply voltage VCC. The supply voltage VCC may be used as an operation voltage in the semiconductor memory device. The boosting voltage VPP may be generated by pumping the supply voltage VCC. The boosting voltage generating circuit may be complemented in the semiconductor memory device. For example, the range of the supply voltage VCC may have a relatively wide scope, for example a scope of 1.5V to 3.8V. Accordingly, the boosting voltage generating circuit may be required to generate a stable boosting voltage VPP under a wider range of supply voltage VCC.
FIG. 1 is a drawing illustrating a conventional boosting voltage generating circuit 10. In the boosting voltage generating circuit 10, a boosting level detection unit 11 may compare the boosting voltage VPP with a target voltage level Vtag(for example 3.6V) and may generate a target level detection signal VDTG. A first boosting pump 13 may pump the supply voltage VCC to increase the boosting voltage VPP depending on the logic state of the target level detection signal VDTG, for example, depending on the level of the boosting voltage VPP. A second boosting pump 15 may be controlled by an active control signal XACT that may be provided from an active response unit 17. The active control signal XACT may be activated in response to an active command ACMD. When the active command ACMD is generated, the semiconductor memory device may be operated in an active mode.
A bus including a modeling parasitic capacitor 19 may transfer the boosting voltage VPP.
The second boosting pump 15 may pump the supply voltage VCC to increase the boosting voltage VPP, regardless of the level of the pumping voltage in active operation. Accordingly, it may be very difficult to make the boosting voltage VPP stable.
For example, if the second boosting pump 15 is designed with lower pumping capacity, the supply capacity of the boosting voltage VPP may be lower when the supply voltage VCC is lower. Accordingly, when a semiconductor memory device is in the active mode, the level of the boosting voltage VPP may be decreased.
If the second boosting pump 15 is designed with higher pumping capacity, the boosting voltage VPP may be stable, if the supply voltage VCC is lower. However, there may be a problem that the boosting voltage VPP may overshoot a target voltage level when the supply voltage VCC is higher.
Accordingly, in the conventional boosting voltage generating circuit 10, it may be difficult to make the boosting voltage VPP stable.